A hypodermic needle is a sharp, hollow needle intended to penetrate or puncture the skin, mucous membrane, and internal organs of humans or animals for insertion or removal of fluids, aerosols, or particulate suspensions. The hypodermic needle is commonly used with a syringe to inject substances into the body or extract fluids from the body. Such needles may also be used to take liquid samples from the body, e.g., for taking blood from a vein in venipuncture.
When a hypodermic needle enters a patient's body, it is invariably contaminated by the patient's blood, body fluids, etc. Following use of the syringe, the hypodermic needle presents a risk to the administering and assisting physicians, nurses, and other health care personnel because the needle might transmit an infection or disease to such personnel if it were to accidentally puncture them. Others susceptible to accidental needle punctures include sanitation workers who later dispose of garbage containing the hypodermic needles. Often, the accidental needle puncture may be so trivial that it remains unrecognized and, thus, untreated until more serious side effects become apparent.
Both healthy and sick people are subject to diagnostic blood drawing, while only sick patients typically receive therapeutic injections. Since there are more healthy people than sick ones, the incidence of accidental needle stick injuries and microbial disease transmission caused by blood drawing devices far exceeds that caused by syringes used for therapeutic injections given to sick persons. In addition, because the needles used for drawing blood have sharp puncturing points on both ends, in contrast to therapeutic syringe needles with a single sharp end, the chance for needle stick injury is normally higher with blood drawing devices.
Automatic retraction of post-use sharp points by hypodermic syringe assemblies with safety engineered devices is an effective way to guard against accidental needle sticks and inadvertent microbial transmission. Heretofore, simple, inexpensive and effective retraction mechanisms have not been made available or adaptable for blood drawing devices. This is especially so because the double-ended needle poses special problems. For instance, when such retraction devices are applied to dual-point hypodermic needles, retraction of the distal sharp end often results in projection and injury potential of the proximal sharp end. Further, the needle may be screwed to the end of the barrel, which makes retraction of the needle difficult or impossible.
The Design Criteria
Improved engineering controls are often among the most effective approaches to reducing occupational hazards, and therefore are an important element of a needle stick prevention program. Such controls include eliminating the unnecessary use of needles, and implementing devices with safety features. A number of sources have identified the desirable characteristics of safety devices [OSHA 1999c; FDA 1992; Jagger et al. 1988; Chiarello 1995; Quebbeman and Short 1995; Pugliese 1998; Fisher 1999; ECRI 1999]. These characteristics include the following:                The device is needleless.        The safety feature is an integral part of the device.        The device preferably works passively (i.e., it requires no activation by the user). If user activation is necessary, the safety feature can be engaged with a single-handed technique and allows the worker's hands to remain behind the exposed sharp.        The user can easily tell whether the safety feature is activated.        The safety feature cannot be deactivated and remains protective through disposal.        The device performs reliably.        The device is easy to use and practical.        The device is safe and effective for patient care.        
Although each of these characteristics is desirable, some are not feasible, applicable, or available for certain health care situations. For example, needles will always be necessary where alternatives for skin penetration are not available. Also, a safety feature that requires activation by the user might be preferable to one that is passive in some cases. Each device must be considered on its own merit and ultimately on its ability to reduce workplace injuries. The desirable characteristics listed here should thus serve only as a guideline for device design and selection.
In light of the foregoing, significant inventive efforts have been devoted to concealing the sharp point(s) of hypodermic needles. One such effort is described in U.S. Pat. No. 5,338,311, entitled “Hypodermic Needle Assembly,” which issued to the inventor of the present invention on Aug. 16, 1994. A needle-syringe assembly is presented with a needle holder carrying the hypodermic needle on a distal end thereof. The needle holder is slidably mounted in a coaxial cavity of the plunger. To retract the needle, a taper lock is disengaged by rotary movement of the plunger relative to the barrel. While preventing rotation of the needle holder relative to the barrel, continued rotation of the plunger causes a lateral arm of the needle holder to ascend through a helical slot in the plunger so that the needle holder retracts into the coaxial cavity of the plunger and the needle is concealed inside the barrel. A similar device is disclosed in U.S. Pat. No. 5,514,100, entitled “Hypodermic Needle Assembly,” which issued to the inventor of the present invention on May 7, 1996.
Other devices include the Punctur-Guard™ device, manufactured by Bio-Plexus, Inc., of Ventura, Calif., USA. In this device, a coaxial tube is inserted inside the post-use hypodermic needle, projecting beyond the sharp point. This avoids the puncture of the skin by sharp bevel, but does not prevent scratching and microbial transmission.
A cap activated device is disclosed in U.S. Pat. No. 5,810,775 (RE 39107), to Shaw, which is entitled “Cap Operated Retractable Medical Device.” In Shaw, a spring is installed in a compressed state under a needle carrier by a tapered co-axial sleeve inside an adapter. When the cover of the adapter is closed, an inner co-axial tube is pushed down to release the needle carrier, allowing the spring to expand and retract the needle carrier into the adapter tube. The Shaw device has many disadvantages. First, the needle is free and likely to fall off when the cap is opened. In addition, the opening at the bottom of the adapter tube remains open, and there is a potential for aerosolization of contaminated blood upon retraction.
Other attempts have been made to resolve the needle stick problem, but a satisfactory solution is still not available. By way of example, in U.S. Pat. No. 5,070,885, to Bonaldo, which is entitled “Disposable Blood Collection Device”, a movable carrier for the double-ended needle is installed within an adapter. The carrier is accessible from outside the adapter via a manual switch that extends through a longitudinal slot on the adapter. The manual switch allows an operator to force the needle carrier proximally, permitting retraction of the needle. Similarly, U.S. Pat. Nos. 4,813,426, to Haber et al., and 4,892,107, to Haber, also install a needle carrier sleeve that is accessible and controlled through a longitudinal slot on the adapter wall, and is controlled manually or by a spring.
U.S. Pat. No. 4,904,242, to Kulli, provides an internal anchor for a double-ended needle, and retracts the needle with an extension spring. U.S. Pat. No. 4,984,580, to Wanamaker, provides a concentric chamber in the nozzle area of the adapter to accommodate the hub of a double-ended needle. Wanamaker's hub is encircled by a compression spring. A spring release mechanism, which is accessed by a window close to the nozzle, retracts the needle when actuated.
A needle device and method of use are described in U.S. Pat. No. 5,193,552, to Columbus, wherein the needle moves out of and into a protective housing, between two operative positions, one of which causes the housing to shield the needle. Each operative position includes releasable locking detents that operate to temporarily hold the needle in one of the positions, the holding force of one detent being less than that of the other. A third position beyond the one that shields the needle in the housing is used to permanently lock the needle in the housing against accidental reuse. The needle device can be used with a blood collection container or a syringe drug delivery container, each one releasably mating with the device during use.
U.S. Pat. No. 6,869,415 B2, to Asbaghi, provides a protective guard that automatically covers the needle after a blood collection procedure has been completed. Prior to the procedure the guard member is restrained on the device in a proximal position to expose the needle, and to thereby facilitate insertion of the needle into a vein of a patient. When a blood collection vial is engaged with the device, the guard member is released to move distally over the needle. As the needle is being withdrawn from the patient, the guard member automatically covers the needle.
U.S. Pat. No. 7,357,783 B2, to Millerd, also describes a blood collection device wherein the entire double-ended needle is pulled into and covered by an adapter. Initially, the needle assembly is advanced and the vein-puncturing needle is exposed to collect blood. Another needle guard remains anchored to the proximal sample-collecting end of the double-ended needle. When a collection tube is forced on the inner sample-collecting end, the latch is released and advances to cover the vein-puncturing needle. At the end of the procedure the sample-collecting sharp end is still bare to cause contaminated needle stick.
U.S. Pat. Nos. 5,346,480, to Hess et al., 5,292,314, to D'Allessio et al., 5,049,136, to Johnson, 4,923,447, to Morgan, and 4,170,993, to Alvarez, are other examples of needle cover devices. Most currently used devices simply cover the external venipuncture tube by a hinged sheath or retracting needle, while leaving the tube-puncturing sharp point exposed and unsafe. In addition, most of the currently available devices are expensive, and are not inherently safe. Many still have the potential of causing accidental needle punctures and microbial transmission. Most must be disposed of in sharps containers, which increases cost, and sharps containers are not available or affordable to ¾ of the world population.